1. Field of the Invention
This invention relates to a method and composition for chemically cauterizing the tissue lining of a human body cavity, particularly the endometrial mucosa of the uterus. More specifically, the methods and compositions of the present invention provide effective cauterization of the endometrium of a mammalian uterus without many of the disadvantages and dangerous features of known intrauterine cauterization techniques.
2. The Prior Art
The following terms as used herein have the meaning given below:
"Necrosis" means the death of cells in a tissue.
"Endometrium" is that portion of the inner lining of the uterus to which an embryo normally attaches and excludes the portions of the uterine inner lining forming the cervix, to which the embryo usually does not attach.
"Cryogenic" is used to refer to temperatures sufficiently low to cause necrosis.
Apparatus and methods for cauterization of the endometrium of a mammalian uterus, useful in sterilization procedures and cancer treatments, are well known. Thermal and cryogenic treatments have been utilized in such cauterization techniques and typically involve either the direct or indirect application of heat or cold to the tissue to be treated.
For example, a laser hysteroscope has been used to cauterize the endometrial layer of the uterus. This laser treatment suffers from several disadvantages. It requires the application of an intense amount of thermal energy to a relatively small area of tissue even though such a large amount of heat may not be necessary to effectively cauterize the tissue. Further, this laser treatment requires the physician to continually re-position the laser under hysteroscopic control used in the treatment within the uterus in order to treat the entire endometrium. Such internal manipulation of a laser hysteroscope within the uterus of a patient is both difficult, requiring a significant level of skill to perform, and potentially dangerous. Accidental puncture of the uterine or tissue wall may result from manipulation of the laser scope within the uterus or body cavity, and tissue layers beneath the endometrium may be burned through the entire thickness if a laser's beam is left focused on one area of tissue for too long a period of time. Electrosurgical endometrial ablation functions on a similar principle and suffers similar risks as laser endometrial ablation.
A variety of alternatives to laser treatment in cauterizing the uterine endometrium are known. In U.S. Pat. Nos. 4,949,718 and 5,105,808 to Neuwirth et al. a method and device for effecting the necrosis of the tissue lining of a mammalian body cavity, particularly the uterine endometrium by heating the liquid contents of an inflated distendable bladder inside the uterine cavity is disclosed. Inflating the distendable bladder inside the uterus allows for contact between the distendable bladder wall and the endometrial lining. However, the distendable bladder is not effective in contacting all of the endometrial lining. Although the distendable bladder may conform to the general shape of the uterus, due to the irregular surface of the endometrial mucosa and the endometrial cavity, the inflated distendable bladder may not contact all of the uterine endometrium.
U.S. Pat. No. 3,924,628, to Droegemueller et al. discloses a method and apparatus for necrosing tissue cells that utilizes an extendable bladder which is inserted in the uterus and filled with a circulating fluid or gas at cryogenic temperatures (referring to temperatures sufficiently low to cause cell necrosis). The bladder disclosed by Droegemueller et al. is maintained in substantially continuous contact with the inner surface of the uterine lining and achieves necrosis of substantially all of the uterine endometrium in a single treatment. Droegemueller et al. disclose the use of liquid nitrogen that vaporizes prior to introduction into the bladder, thereby pressurizing the bladder to a level which ensures adequate contact with the uterus. Other fluids disclosed by Droegemueller et al. as useful in their method include refrigerants such as freon. Droegemueller et al.'s method and apparatus suffers from the disadvantage of employing cryogenic fluids which are toxic and could prove fatal to a patient in the event of bladder rupture. Moreover, Droegemueller et al.'s apparatus does not allow regulating the pressure used to inflate the bladder. In the event of a bladder rupture, the cryogenic fluid would rapidly change state from a liquid to a gas with possible grave consequences for the patient. Another disadvantage of Droegemueller et al.'s technique is that it does not limit the amount of cryogenic fluid that would be introduced into the uterus in the event of a bladder rupture.
In U.S. Pat. No. 2,734,508, Kozinski discloses a therapeutic apparatus for applying dry heat to body cavities comprising an applicator that is introduced in the body cavity while deflated and which is subsequently inflated and heated by means of circulating hot air. Kozinski does not disclose an applicator which conforms to the shape of a body cavity. Further, given the lower heat transfer coefficients of gases as compared with liquid, treatment with Kozinski's apparatus should involve a long period of time in order to achieve necrosis, thereby exposing the patient to additional discomfort and risk. Moreover, Kozinski's apparatus does not provide for measurement and regulation of internal pressures and temperatures of the applicator introduced.
U.S. Pat. No. 2,077,453, issued to Albright, discloses a therapeutic appliance comprising a relatively long tubular applicator which is shaped and formed generally to the passage into which it is to be inserted and which has relatively thin elastic rubber walls that transfer heat and which distend to fit irregularities of the treated areas upon application of internal pressure. Albright also discloses that fluids such as heated water could be utilized as a heating means in his applicator. The applicator of Albright, like that of Kozinski, however, suffers from the disadvantage that the distension of its walls to conform to the irregularities of the endometrium is limited as Albright provides an integral rubber web which serves to prevent undue distension of the applicator. Moreover, Albright requires that the fluid be circulated throughout the apparatus. Albright also does not provide an apparatus that allows regulation of temperature and pressure of the fluid or other bladder inflation means.
U.S. Pat. No. 3,369,549, issued to Armao, discloses a therapeutic device for applying heat or cold to body cavities comprising a capsule probe containing a heat exchanger and a flexible bladder that can be inflated to conform to a body cavity. Armao does not, however, disclose a control means for regulating the temperature and pressure of the flexible applicator, nor does he disclose cauterizing tissue in the cavity being treated.
Other patents that disclose the use of thermal treatment of the interior lining of a body cavity include U.S. Pat. Nos. 2,192,768; 2,466,042; 2,777,445; and 3,369,549.
In addition to these thermal and cryogenic treatments, application of caustic chemicals to achieve sterilization and treat cancers is also known. The use of caustic chemicals as locally destructive agents has been attempted but has been limited by concerns about safety and control of the delivery of various agents as well as other shortcomings due to the methods of application, e.g., blind placement of a particular solid chemical. For example, as described by Babcock, W., Chemical Hysterectomy, Jnl. Obstet. & Gyn., Vol. 7, 1924, application of gauze strips soaked in a saturated solution of zinc chloride to the uterine walls has been used to produce amenorrhea, to produce sterility, and to treat tumors. However this procedure has several disadvantages. Initially, it is noted that the application of the gauze strips is a blind procedure. The zinc chloride soaked gauze is packed in the uterus until the practitioner feels the cavity is full. The strips are left in place for a predetermined length of time and then removed. Delivery to and removal from the uterine cavity of the caustic gauze strips necessarily entails substantial risk of contacting the vaginal walls wherein the caustic agent could damage the vaginal and other tissue which is not the target of the treatment. Accordingly, successful use of this methodology requires substantial skill and experience, limiting the availability of the procedure to women with access to highly trained medical personnel.
Use of caustic agents such as silver nitrate, zinc chloride and copper sulfate has been studied for use in chemical sterilization by chemically cauterizing the fallopian tubes. However, as discussed by Richart, R., Female Transcervical Sterilization, Chapter 3, Harper & Row (1983), even when massive tubal necrosis was achieved with the application of silver nitrate (AgNO.sub.3), a significant proportion of fallopian tubes remained open. When compositions for the sustained release of the caustic agents were employed it was found that control over the release of the caustic agents was insufficient to avoid unacceptable side effects. Additionally, use of strong caustic agents such as acids and alkalies would require the concomitant use of equally strong neutralizing agents whose use is also laden with risk. Use of such agents also puts the practitioner in the difficult position of titrating the neutralization of the caustic agent in the patient's uterus.